Kadioglu Aras, Taylor Sally, Iannelli Francesco, Pozzi Gianni, Mitchell Tim J, Andrew Peter W
Department of Microbiology and Immunology, University of Leicester, Leicester, LE1 United Kingdom.
Infect Immun. 2002 Jun;70(6):2886-90. doi: 10.1128/IAI.70.6.2886-2890.2002.
Pneumococci frequently colonize the upper respiratory tract, and these pneumococci are believed to act as a reservoir for infection of the lower respiratory tract and bacteremia. We investigated how the pneumococcal toxin pneumolysin affects the capacity of pneumococci to infect the upper and lower respiratory tract of the mouse. Wild-type Streptococcus pneumoniae serotype 2 and 3 strains, a serotype 2 pneumolysin-deficient mutant, and a serotype 2 mutant with the pneumolysin gene reinserted were used to study differences in colonization and disease. In addition, we also examined a pneumococcal chimeric mutant (capsule type switched from serotype 2 to serotype 3) to gain further insight into the role that capsule plays in nasopharyngeal infection. Absence of pneumolysin was found to be associated with significantly lower numbers of pneumococci in the nasopharynx, trachea, and lungs. Differences in pneumococcal capsule type were found to have significant effects on pneumococcal infection of the nasopharynx, trachea, and lungs. However, it was the combination of capsule type and genetic background that was important, and the influence of this combination varied with the site of infection. For example, in the nasopharynx the wild-type serotype 3 strain and the capsule-switched mutant behaved similarly, whereas in the lungs the mutant that was switched to serotype 3 survived less well than the wild-type serotype 3 strain. The combination of capsule type and genetic background also determined virulence. Thus, the wild-type serotype 3 strain was virulent, whereas the capsule-switched mutant was avirulent.
肺炎球菌常定殖于上呼吸道，这些肺炎球菌被认为是下呼吸道感染和菌血症的感染源。我们研究了肺炎球菌毒素溶血素如何影响肺炎球菌感染小鼠上、下呼吸道的能力。使用野生型2型和3型肺炎链球菌菌株、一株2型溶血素缺陷型突变体以及一株重新插入溶血素基因的2型突变体来研究定殖和疾病方面的差异。此外，我们还检测了一株肺炎球菌嵌合突变体（荚膜类型从2型转换为3型），以进一步了解荚膜在鼻咽感染中所起的作用。结果发现，缺乏溶血素与鼻咽、气管和肺部肺炎球菌数量显著减少有关。肺炎球菌荚膜类型的差异对鼻咽、气管和肺部的肺炎球菌感染有显著影响。然而，重要的是荚膜类型和遗传背景的组合，并且这种组合的影响因感染部位而异。例如，在鼻咽部，野生型3型菌株和荚膜转换突变体表现相似，而在肺部，转换为3型的突变体比野生型3型菌株存活能力更差。荚膜类型和遗传背景的组合也决定了毒力。因此，野生型3型菌株具有毒力，而荚膜转换突变体无毒力。
